BT reveals 300Mbps G.fast trial routers, some with “reverse power”

Openreach G.fast trial has been a success. Roll-out coming over the next few years.

BT Openreach's trial of G.fast, which will eventually bring download speeds of 300Mbps to millions of plain ol' copper telephone lines over the next few years, is drawing to a close in Swansea, Huntingdon, and Gosforth. Back in September, BT said that the trial has been a big success, with "almost all" homes getting 300Mbps down and 50Mbps up. Now, BT has revealed some details about the G.fast modems and routers being used for the trial.

In total, according to ISP Review, four modems/routers are part of the trial: the Huawei MT992 (in Huntingdon), Zinwell zGFS-1001C (Huntingdon), Technicolor TG799vac Xtream (Huntingdon), and the Alcatel-Lucent F-240W (Gosforth). Curiously there's no mention of what equipment is being used in the Swansea trial.

The Huawei unit appears to be very similar to the Openreach VDSL modem, but with a G.fast chipset ensconced within instead. It looks like it would be plugged into some kind of wired or wireless router. The Zinwell device is a combi-modem-and-router, based on the Sckipio G.fast chipset. The Technicolor thing is again a combi-G.fast-modem-and-router, as is the Alcatel-Lucent doohickey.

The Alcatel-Lucent G.fast modem/router, also with the "reverse power" feature.

The Zinwell and Alcatel-Lucent devices do have one stand-out feature, however: reverse power. With ADSL and VDSL (i.e. "superfast" broadband), Openreach's equipment draws power from the green cabinet or a nearby exchange. With G.fast, however, Openreach is looking at powering its equipment by sucking power from your router.

This might sound a little crazy, but it does make a surprising amount of sense. Basically, the max range of G.fast is only a few hundred metres. VDSL/FTTC, however, is good up to about 1 mile (1.6km). With VDSL, Openreach usually puts all of its hardware in a green cabinet, which could be much farther than a few hundred metres from your house—too far for G.fast.

G.fast bandwidth usage vs. VDSL (FTTC). G.fast uses a lot more bandwidth, but as a result the signal attenuates over a much shorter distance - thus the node/distribution point has to be closer to the end point.

Further Reading

The solution is to put a G.fast node closer to your house, either on a telephone pole or down a manhole. There are a few ways to power these G.fast nodes, but one of the simplest is to take some power from a nearby G.fast customer. There hasn't been much discussion of it yet, but presumably Openreach would repay the home or business owner for the electricity consumed in this way.

The use of all-in-one modem/router hardware for the trial suggests that Openreach will be pursuing a self-installation path for G.fast customers, much like with the current rollout of VDSL/FTTC.

There's no word yet on final hardware, G.fast products (presumably there will be various tiers with 300Mbps at the top), or pricing. The current plan is to roll out G.fast to 10 million UK premises by 2020, and then "most of the UK" by 2025. G.fast can theoretically scale up to 500Mbps, or perhaps a little faster, but the initial plan is to cap the downlink speed at 300Mbps.

Sebastian Anthony
Sebastian is the editor of Ars Technica UK. He usually writes about low-level hardware, software, and transport, but it is emerging science and the future of technology that really get him excited. Emailsebastian@arstechnica.co.uk//Twitter@mrseb